1. Field of the Invention
This invention relates to the process for separation of a proteinaceous gluten from wheat flour and is particularly directed to the separation of a proteinaceous gluten having a high protein concentration above 80% from wheat flour whereby the gluten is recovered in a non-denatured and vital form. This invention is particularly directed to a process for the separation of highly proteinaceous gluten from wheat flour by a continuous process which does not require substantial amounts of water. This invention is also directed to such a process which can be carried out in a minimum period of time and without substantial mechanical working of the masses involved in the processing.
2. Discussion of the Prior Art
The separation of wheat flour into its component parts, starch and gluten, is well known. Kerr in Chemistry and Industry of Starch, second edition (1950) and Knight in The Chemistry of Wheat, Starch and Gluten and Their Conversion Products (1965) both review the processes which had been involved. Essentially, the early commercial embodiment for the separation of wheat flour in its components was the Martin method, which commenced in about the year 1835. The Martin method is still almost exclusively used industrially in its various applications. Essentially, it involves initially forming a dough by mixing wheat flour with a small quantity of water. After a suitable resting time, the dough is kneaded with simultaneous continuous addition of water. The starch is thus gradually washed off from the elastic gluten whereby both the starch and the gluten eventually are separated from each other in very pure fractions. The method however requires the use of large quantities of water, generally 10-17 fold water per quantity of flour. Additionally, usually about 8-10, and even up to 20%, of the dry content of the flour is lost in the diluted waste water. Obviously, this presents a considerable problem commercially. Even in its best forms, the water content of the Martin process has been reduced to 6 fold the flour quantity.
Other methods have been proposed. One such method is known as the modified Fesca process and is described by Fellers et al. in "Process for Protein-Starch Separation in Wheat Flour", (1969), Food Technology, volume 23, 162-166, and Johnston et al. in "Process for Protein-Starch Separation in Wheat Flour", 1971, Journal of Food Science, volume 36, 649-652. Another process is known as the "batter process" and it is described by R. A. Anderson et al. in "Continuous Batter Process for Separating Gluten from Wheat Flour", (1958), and later in 1960 in an article entitled "Pilot Plant Studies on the Continuous Batter Process to Recover Gluten from Wheat Flour". The first article is found in Cereal Chemistry, volume 35, 449-457, and the latter is found in that same journal, volume 37, 180-188. These processes have in common the initial step directed to preparing a free-flowing smooth slurry or batter having a small water/flour ratio.
In the Fesca process, the desired slurry temperature is about 30.degree.C while in the batter process, higher temperatures, e.g. 40.degree.-55.degree.C, are employed. These temperature differences constitute one of the basic differences between the two processes.
In the Fesca process, it is desired to prevent the gluten from hydrating, or coalescing, so that pure prime starch can be centrifuged directly from the slurry leaving a liquid protein concentrate fraction. This is in direct contrast to the batter process, where after initial slurry preparation, the addition of a second increment of water and the higher temperature results in an almost instant gluten hydration. Once the gluten is coalesced, it is shredded in a cutting pump, the occluded starch washed out, and the gluten recovered on the screen where it is further washed. The filtrate, or remaining slurry, is further fractionated to yield prime starch, low grade starch, waste fiber-gluten solids and waste solubles in the liquid effluent. In the Fesca process, all of the flour constituents are recovered in the two resulting products: prime starch and a protein concentrate of 20-40% protein content. No provisions thus far have been made to separate the gluten from the liquid protein concentrate in a purified state.
In an older process described by Burdick in U.S. Pat. No. 2,504,962 (Apr. 25, 1950), the same principle of the batter process is utilized until screening of the gluten. The screenings, or crude gluten, is then agitated and aerated with three parts of additional water to beat thoroughly the starch and bran from the gluten and produce a gluten foam which is then separated by flotation.
In still another process described by Walsh et al. in U.S. Pat. No. 2,572,225 (Oct. 23, 1951), the principle of the Martin process is employed but the elastic dough is repeatedly drawn out or stretched into long strings or ropes so as to expose a maximum surface to the washing action of the added water. The gluten is recovered in a de-natured or non-vital condition.
It has become an object of this invention, therefore, to provide an improvement over the Martin process, wherein small quantities of water relative to the amount of flour can be employed to separate the wheat flour into the starch and gluten. It has also become desirable to provide a process wherein the formation of an elastic dough or the like is not involved, whereby the mechanical working of the mass is held at a minimum. Still another object of this invention is to provide a process for the separation of wheat flour into its components, whereby a highly proteinaceous gluten is obtained, which is neither de-natured nor in a non-vital condition. It has become still a further object of this invention to provide a process whereby use of operation, and flotation processes are not required. Moreover, it has become desirable to provide a process for the preparation of a gluten having a protein content of at least 80%.